1. Field of the Invention
The invention relates to a developer, an image forming unit, and an image forming apparatus.
2. Description of Related Art
In an image forming apparatus such as a copy machine, a facsimile machine, an MFP (multi-functional printer or multi-functional peripheral) and the like, for example, in a printer, a charging roller uniformly charges a photosensitive drum, and an LED head exposes light onto the charged photosensitive drum to form an electrostatic latent image on the charged photosensitive drum, and a developing unit develops the electrostatic latent image to from a toner image on the charged photosensitive drum. The developing unit includes a developing roller, a toner supplying roller, a development blade, and the like. In the developing unit, the toner supplying roller supplies toner serving as a developer to the developing roller, the development blade meters the toner on the developing roller to form a thin toner layer on the developing roller. The toner on developing roller is attracted to the electrostatic latent image on the photosensitive drum so that the toner image is formed on the photosensitive drum.
Then, a transfer roller transfers the toner image from the photosensitive drum to a paper sheet, and a fixing unit fixes the toner image to the paper sheet.
In the printer, an image forming unit is composed of the photosensitive drum, the charging roller, the developing roller, the toner supplying roller, the development blade and the like. When just one of the photosensitive drum, the charging roller, the developing roller, the toner supplying roller, the development blade, and the like reaches the end of its life, a printer controller determines that the image forming unit reaches the end of life. The entire image forming unit is then replaced with a new image forming unit.
Over a long period of time, the toner may become degraded by being rubbed and/or pressed by means of the developing roller, the toner supplying roller, the development blade, or the like. Depending on the condition of use of the printer, the toner property may not last until the end of life of the image forming unit.
To overcome this problem, a printer capable of preventing such toner degradation by using a toner whose glass-transition point (glass-transition temperature) is equal to or greater than 75° C. is provided (for example, Japanese Patent Application Laid-Open No. 11-242355).